Reaction product of diphenylolpropane diglycidyl ether with styrene-acrylic acid copolymers



Patented July 22, 1952 REACTION PRODUCT or DIPHENYLOLPRO- PANE DIGLYCIDYL ETHER WITH STY- RENE-ACRYLIC ACID COPOLYMERS Gordon Hart Segall and John Francis Clemow' Dixon, McMasterville, Quebec, Canada, assign:

ors to Canadian Industries Limited, Montreal, Quebec, Canada, a corporation of Canada,

- No Drawing. Application May 31,1951, Serial No. 229,291. In Canada March 3, 1949 This invention relates to new polymeric matee rials and to a methodof making the same. More particularly, it relates to thermoset, infusible, solvent insoluble polymerspf styrene having an intermediate thermoplastic, fusible, solvent soluble stage, and to a method of making the same. Still more particularly, it relates to, such polymers for usein the protective coating field.

This application is acontinuation-in-part of our application Serial No. 168,146 filed on 14th June, 1950, whichis itself a continuation-in-part of our application Serial ,No. 132,204 filed 9th December, 1949, both now abandoned.

It has heretofore been the practice to prepare thermoset, infusible, solvent insoluble polymeric materials from styrene bycopolymerizing styrene with divinyl bfenzene," However, due tow the identical activityof' the (vinyl bonds in the divinyl benzene, it has been impossible to obtain a thermoplastic, fusible, solvent-soluble product at any stage of the copolymeriza'tion except at very low conversions. Cross-linking occurs simultaneously with linear polymerization and the end product is highly cross-linked and hence thermoset, infusible and solvent insoluble., v

Theproduction of protectivecoatings based on thermoset, infusible, solvent insoluble polymeric materials, for example, preferably requires that a thermoplastic, fusible, solvent soluble product be formed at an intermediate stage of the polymerization reaction. The thermoplastic product may thus be homogeneously and uniformly applied to the articles to be coated, and thereafter infusibilized and insolubilized by baking.

If, instead of divinyl benzene, a vinyl monomer containing a less active double bond, e. g. a vinylallyl compound, is copolymerized with styrene, it is possible, by" careful control of polymerization conditions, to'obtain alinear. thermoplastic styrene copolymer which subsequently can be infusibilized and insolubllized by cross-linking through the allyl group. However, since an allyl group difiers from a vinyl group only in the degree with which it polymerizes, it is diflicul't to exclude the possibility of cross-linking during the initial polymerization. Accordingly, the-range of polymerization conditions is seriously limited and there is a constant danger of gelation with loss of the polymer charge.

' ,It has now been found that if styrene is copolymerized with a certain minor amount of an acrylic acid, with or without a minor amount of. another polymerizable ethylenically unsaturated compound having the ethylenic group assole reactive group-audit ;the,re s' ultant; copolymer is heated 10 Claims. (Cl. 260-805) with diphenylolpropane diglycidyl etherunder the conditions hereinafter specified, the above difiiculties are completely overcome, There is first obtained a thermoplastic, fusible, solvent soluble copolymer which is substantially free of any cross-linkage and which becomes thermoset, infusible, solvent insoluble by cross linking through its free carboxylic acid groups only upon reaction with the diphenylolpropane diglycidyl ether. Any polymerization conditions can thus beemployed for preparing I the thermoplastic copolymer and there is absolutely no danger of gelation occurring during the initial polymerization. j

This particular type of thermoset styrene polymer has been found very suitable for use in moulding operations and in the protective coating field. Furthermore, it has been found that if a certain minor amount of a lower-alkyl ester of acrylic acid is incorporated into the styreneacrylic acid copolymer, this copolymer yields upon heating with diphenylolpropane diglycidyl ether under the conditions hereinafter specified protective coatings which are markedly superior to other known coatings based on thermoset, infusible, solvent-insoluble polymers and, more particularly, to the alkyd-type protective coatings.

In United States Patent Nos. 2,375,960 and 2,421,876 and German Patent No. 544,326, it has been proposed to copolymerize styrene with an unsaturated anhydride, such as maleic anhydride, and to infusibilize and insolubilize the resultant thermoplastic copolymer by reaction with a polyhydroxy compound, such as a glycol or glycerol.-

In such instances, free carboxylic acid groups are formed as a result of the cross-linking reaction, which'results in alkali sensitivity of the thermoset polymers and hence of protective coatings based on these polymers, whereas inthe process ofthe present invention, free hydroxyl groups are produced which do not aifect the alkali resistance of the polymers or of the protective coatings based thereon. Furthermore, it is difiicult to produce copolymers containing maleic anhydride or other unsaturated anhydride which have a wide range of composition because of the tendency of these materials to polymerize in constant proportions with other monomers. This diificulty is not encountered in the process of this invention.

French-Patent No. 881,981 shows the reaction between polyepoxides and polymeric materials containing free carboxylic acid' groups with resultant cross-linking of the polymeric materials. Under the conditions, defined in? the patent, however, the cross-linkage isxnottsufficiently high to vention will be apparent by reference to the following specific examples, it being understood that these examples are merely illustrative embodiments ofthe invention and; that the scope of the invention is not l-ilni-tedthereto'.

' Example 1 A solution of a 95% styrene-5% acrylic acid copolymer was prepared by dissolving 475 parts free carboxylic acid groups although they are satisfactory for partial cross-linking of such polymers. Moreover, as above mentioned, despite the efiiciency of diphenylolpropane diglycidyl-ether for completely thermosetting styrene-acrylic acid copolymers under the conditions; hereinafter specified and thus yielding many. valuable prod! V V ucts, the presence of a specific amount of a third component in the styrene copolymer is necessary for obtaining the superior metal finishes above referred to. The partially cross-linked'polymers of French Patent No. 88 ,981 are very suitable for such usesas the thickening of solutions, but they are unsatisfactory for use as protective coatings and for the manufacture of moulded articles which require a'high'chemical inertness. The present invention provides the-means whereby polymers are-obtained which are completely'thermoset,-infusib1e and solvent insoluble and yet possess a definite intermediate thermoplastic, fusible and solvent soluble stage, and whereby protective coatings arealso obtained which possess physical and chemical properties hitherto unknown in protective coatings based on thermoset polymeric materials.

It is thereforean object of this invention to provide new and useful polymeric materials.

Another object-of this invention is to provide styrene polymers having improved properties.

A further object of this invention is to provide thermoset, infusible, Solvent insoluble polymers of'styrene having an intermediate thermoplastic, fusible, solventsoluble stage.

- A'still further object of this invention is to provide such styrene polymers for use in the protective coating field.

An additional object of this inventi'on is to provide a-method for preparing these polymers.

Other and additional objects of the invention willbecome apparent hereinafter.

These objects are accomplished by copolymeriz ing more than 50 parts of'styrene with at least 5 parts of an acrylic acid, with or without another polymerizable ethylenically unsaturated compound having the ethylenic group as sole reactive group, the total parts being 100, and subsequently heating and resultant thermoplastic, fusible, solventsoluble copolymer with diphenylolpropane diglycidyl ether at a temperature of about 150C. in the presenceof at least 0.5%, by weight of the 'copolymer, of an organic basic catalyst selected'from thegroup consisting of I amines and quaternary ammonium compounds. 7

By copolymerizing morethan 50 parts of sty rene with at least 5 parts of an acrylic acid and at least parts of a lower alkyl ester of acrylic acid, the total parts being 100, and subsequently heating the resultant thermoplastic c'opolymer with diphenylolpropane diglycidyl ether under the conditions above defined, protective coatings are obtained whichpossessphysical and chemical properties: hitherto unknown in protective coatings based on thermoset polymeric materials.

The. details and manner ofpractising the inof styrene and 2.5parts of acrylic acid in 25 parts of amyl acetate and 25 parts of high boiling aromatic hydrocarbon, and heating at 90 C. for 16 hours ill-the presence of 1 part of benzoyl peroxide. 7

To 5 parts of the above solution, there was added 0.625 part ofdiphenylolpropane diglycidyl ether (prepared by interaction of phenol with acetone in the presence of an acid catalyst, followed by reaction with an excess of epichlorohydrin in the presence of aqueous caustic) together with 0.05 (-2%" byweight of the copolymer) of trimethylbenzyl ammonium acetate, and

a film was cast therefrom'." After: heating at' 156?- C. for 30 minutes, the film was insoluble in acetone which is a' solvent for the initial styrene copolymer. 1

Similar results were obtained by use of diethylene triamine: and piperidine. instead oftrimethylbenzylammonium acetate.

A copolymer of styrene and acrylic acid containing less than 5% acrylic acid would" not yield an acetone-insoluble: film 1 under the above treatment. 1

Example 2- A solution of a styrene 15%, acrylic acid copolymer was prepared by dissolving 430 parts of styrene and 76 parts of acrylic acid in a mixture of 253. parts ofamyl, acetate and-253 parts of high boiling aromatic hydrocarbon, and heating at C. for 24 hours in the presence of 10.12 parts of benzoyl peroxide.

Ethyl acetate was added. to the above copolymer solution so as to make a solution containing 3 parts of amyl acetate, 1 part of. high boiling aromatic hydrocarbon and 1 part of ethyl acetate. '8 parts of this solution were then mixed with 2 parts of. diphenylolpropane diglycidyl ether and 1% by 'weightof. the copolymer, of piperidine, and a .filmwascasttherefrom on. base steel; After heating at 150 C. for. 30 to 40min? utes, this film was insolubleinacetone.

Example 3 127.5 partsof'styrene and; 22.5 partsof, meth-' acrylic acid in parts ofmethyl ethyl ketone and 50' parts of xylene were copolymerized by heating at 90 C. for 24 hours the presence of 3 parts ofbenzoyl peroxide. There wasthus obtained a solution of a copoly ner containing 85% styrene and 1.5%methacry1icacid,

To 5 parts of' the' aboyesolution there was added 0.45; parts of diphenylolpliq ane. diglycidyl ether together with 0.025 parts (1% by weightof the copolymer); of' piperidine a fil n ,was cast therefrom. After heating. at 1505C. for 1 .5'hours, this film was insoluble in acetone; iv 7 Eramplc 4 127.5 parts of styrene and 22.5 partsof meth acrylic acid were copolymerizedin "100- parts of methyl ethyl ketoneand-50 parts of xylene by heating at 90C. for-24 hours-inthe presence of 5. parts of the copolymersolution were then.

mixed: with 0;625- part "of diphenylolpropanemethyl acrylate-8% acrylic acid copolymer solution containing 50% total solids.

To 1600 parts of this solution were added 200 parts of diphenylolpropane diglycidyl ether and parts or trimethylbenzylammonium acetate.

An enamel wasprepared by dispersing 1000 parts of .titanium dioxide pigment in a roller mill in a portion oi the above mixture and after com- 2 plete dispersion, the remainder of the mixture was added and. thoroughly mixed.

This composition, when applied .to a rigid steel surface and baked for 60 minutes at 150 C., produced a high gloss white enamel coating having an excellent flexibility and durability and having a water, alkali, grease. and organic solvent resistance superior tothat oi the alkyd-type coatings.

Example 6 A white enamel composition" was prepared fol; lowing the procedure outlined in Example 5. Prior to the application of the enamel to a metal surface, 0.25% of polymerized ethylene was added as a 10% solution in toluene; This produced a finish with improved mar resistance in addition to the desirable 'features referred to in the precedinge'xamp'le'. Q

Example 7 A copolymer. containing 85% styrene, 10% methyl acrylatejand 5% acrylicacid was prepared by heating ,42.5, partsjoi styrene with 5 parts of methyl acrylate and 2.5 parts of acrylic acid in 50 parts of toluene-containing 1 partof benzoylperoxide, at 90 C. for 18 hours.

To 5 parts oi'--theabove solution, there was added 0.625 part. of diphenylolpropane diglycidyl ether together with 0.025 part (1%-by Weight of the copolymer) of trimethylbenzyl ammonium acetate and a=-film was cast therefrom. After heating at150' C. for minutes, this film had a chemical inertness similar to that or the film obtained in Example 5- but--it wasmore brittle than that film'orysi'milar films obtained from alkyd-type resins.

part of diphenylolpropane diglycidyl ether and 0.01 part (0.8% by WQight of the copolymer) of piperidine and aiilm was cast from the solution. After. heating';at 150 .c. for one hour, the film had thesame properties as the film obtainedin Example 5. 1.1; 5. i

6 U Similar results were, obtained by using 0.5% (by weight of'the copolymer) of piperidine instead of 0.8%. 1 However, ru e of less than 0.5% we l m l dan in o u e fllm- I;

. l -Example 9 8.74 partsfof styrene,v 1.88 parts or acrylonitrile and 1.88 partsvof acrylic acid in 2515 'parts of methyl ethyl ketone and 12.5 parts of xylene were 'c'opolym'erizedby heating at a temperature of C. for 24 hours'using 0.25 part ofbenzoyl peroxide catalyst. There was thus obtained a solution of a 70%' styrene-15% acrylonitrile- 15% acrylic acid copolymer. v

To 5 'parts'of the above solution, there was added 0.8 part of diphenylolpropane diglycidyl ether together with'0.01 part (0.8% by weight of the copolymer) of piperidine and a film was cast therefrom on autobody steel panels. After heating at C. for one hour, the film was insoluble in acetone. v I I The above-detailed examples illustrate certain embodiments of the invention wherein there are completely infusibilized and insolubilized specific styrene copolymers containing specific acrylic acids, with or without specific polymerizable ethylenically unsaturated compounds having the ethylenic group as sole reactive group. The present invention, however, is not restricted to such specific acids and compounds.

The acrylic acids which can be incorporated into the styrene copolymers' include such acids as acrylic acid, haloacrylic acids, methacrylic acid and crotonic acid.

The ethylenically unsaturated compounds include any such compounds provided only that.

they are polymerizable and containthe ethylenic group as sole reactive group. Illustrative compounds which .can be used are acrylic, halo-' acrylic, methacrylic .esters and nitriles,.such as, for. example, acrylonitrile, methyl methacrylate, butyl methacrylate, octyl methacrylate, methoxymethyl methacrylate, chloroethyl methacrylate, and the corresponding esters of .acrylic .acid alpha-chloroacrylic acids; .vinyl and vinylidene halides, e. g..-vinyl chloride, vinylfiuoride, vinylidene chloride, vinylidene fluoride; vinylcarboxylates, e. g. vinyl acetate, vinyl chloroacetate vinyl propionate and vinyl stearate; vinyl aryls, e. g. vinylnaphthalene; methyl vinyl ketone, etc.

The lower alkyl esters of acrylic acid which are necessary for the obtention of the above-mentioned superior protective coatings include such esters as methyl acrylate, ethyl acrylate, propyl acrylate and butyl acrylate.

For the preparation of the thermoplastic, fusible, solvent solublestyrene copolymers, any of the well-known processes for the copolymerlzation of styrene can be used. The previous examples illustrate a solution copolymerization method which is preferable when it is desired to thermoset the copolymers as protective coatings.

For optimum results, the diphenylolpropane diglycidyl ether should be present in an amount of one mol for each two free carboxylic acid groups of the thermoplastic copolymers to be usedin the cross-links.

Any organic amine or quaternary ammonium compound can be used as acatalyst for the infusibilization and insolubilization of the thermoplasticstyrene copolymers. Examples of such suitable catalysts are pyridine, piperidine, dimethyl aniline, diethylene triamine, tetramethylammonium. chloride; .trimethylbenzylammonium acetate; etc. in; the :proportion of 0.5-2.0% by,

aic o ikie i weight}of thethermoplastic copolymer to be infusibilized and ins'olubilized.- v

In the example ofthe pigmented'composition described above, titanium dioxidewas'used as the pigment constituent. Other pigments may alsobe used in the compositions either alone or in admixture jto pr'oduce enameljs' of. various colours; These compositions" are, i however'y of particular value when produced with" white pigments since they are highly resistant" to yellowingon*loa l :in'g.*v v i, Ass hown in" thefo'regoing, examples, the finfusibilization andinsolubilization can be obtained in articles produced from: a: solution containing a common solvent 'for and in which the thermoplastic-Jumble, solvent soluble copolymer and the diphenylolpropane" diglycidyl ether are compatible: Such solvents include, for example, esters", ketonesand mixturesof hydrocarbonswith esters and/or ketones; However, the infusibilization and insolubilization can beconducted also on a preformed thermoplastic, fusible, solvent soluble polymeric article." I V The inventtion provides a simple-and easilycontrolle'd' process for obtaining thermoset, infusible, solvent insoluble polymers of styrene-having an; intermediate thermoplastic, fusible, solvent soluble stage; The process does notfgiv'e rise to the formation-of undesirable by proclucts', the thermoset polymeric product 1 finally obtainedbeing free 'ofundesirable substances. J Thegthermoseu infusible; solvent insoluble styrene polymers of this invention are adapted for a wide variety of uses. For example, they are suitable/as. adhesives, laminates, protective coatings and for the production of moulded plastic articles andlike outlets. having a high-chemical inertness- Plasticizers, pigments, dyes, reinforcing agents and like materialacommonly used in 1 formulating polymeric compositions can be used.

As above .mentioned. some. .of. the thermoset polymerssofi: thisinvention yield protective coatingszhaving; physical: and chemical properties hitherto unknowneinprotective: coatings based on thermostatpolymericrmaterialsa. 1

.since itz'is'.obviousuthatmany' changes and; modificationsl'cansbe made: inithe; above-described. detailswithout; departing from: the. nature. and; spirit of:the.invention;it.is to beunderstoodlthat the invention is nofmt'o be. limited. thereto except as. setiorth in; the appended. claims;

- Having .thusu'described. our. invention, what; we

claimisz. o

. 1., A process for: the preparation of 'thermoset, infusible, solvent insoluble polymers of styrene, which compriseseheating a.thermoplastic;,fusible, solvent. soluble copolymer containing. essentially more than 50 partsv ofistyrene and at:least.5oparts of anacid selected from the: group. consistingof: acrylic acid and methacrylio acid, the. total. parts. being. 100, vwith: one mol oi. diphenylolpropane. diglycidyl GthBI'iQX'JeZBhVtWO fiBB carboxylic acid groups; of. the; copolymer; ata temperature of about 150?" C; and; in the presence. of. at. least, 0.5%, by'weight ofthecopolymer, of an organic basic catalyst selected iromthegrou consisting, of amines and quaternary ammonium; come pounds. 5

. 2. A process forrthe preparation. otthermoset, infusible, solvent'i'nsoluble polymers-of. styrene,

. 7 which comp'rises1heating:a thermoplastic; fusible;

solventsoluble copolymer of from '10 to: $.parts of styrene and ircm 5150 15 paiztszofian acid: sele'cted.from.thegroupiconsistingf of acrylicacid.

and niethacrylic acid andfrom o toauiparts of; 5,: the f copolymer, of an organic basic; catalyst.

quaternary ammonium compounds;

another ,poly'mjcrizabj1e jmonoethyl'enically unsaturated compound having the ethylenic group as. sole reactivegroup', the total parts being 100, with one mol of diphenylolpropane diglycidyl ether for each two free carboxylic acid groups of the copolymer at a'temperature of about C. and in the presenceof at least 0.5%, by weight of the; copolymer, 1 of an organic basic catalyst selected fromtliezgroup consisting of airlines and 31 A ip'rocess 'for the preparat'on of theri'noset, infusi'ble, solvent!insoluble'polymers of styrene suitable as protective "coatings, which comprises heating a thermoplasticfusible, solvent soluble copolymer of mcre tha'n 50 parts of styrene and at Iea's'tIB-partsofan acid selec'tedfrom the group consisting or some acid. and. methacrylic acid and at least-"15 parts of a lower alkyl'ester-of acrylic acid, :the-total parts' being 100'; with one mol 1 of :diphenylolpropane :Tdiglycidyl other 'for' eachtwoifree carboziyllic acid groups of the copolymer, at a temperature:of.about'150 C. and.v in the presence of at'least 0.5%, by weightot the copolymer; of an organic basic catalyst selected fromthe group consisting zof aminesand quaternary: ammoniumcompound's. r

4. A process for the: preparation of: thermoset, infusible,;'solvent insoluble. polymers. of styrene. suitable as protective coatings, which comprises heating a thermoplastic,: fusible, solvent soluble copolymer of. from.'l0 to. 80 parts. of styrene. and from 5. to I5 arts 'oran acid selected from the group: consisting. of acrylic acid and. methacrylic acid 'arid from 15 to. 20 partsor a loweralkyl ester of acrylicgacid, the total parts being 100, with. one mol' of .fdiphen'ylolpro'pane diglycidyl ether for each two freefcarboxylit:'acidigroups of the copolymer, at a temperature of about 150.. C. and in the presence of at least 0.5%, by weight'of the copolymer, of an. organic basic catalyst selected from the grou consisting of amines andquaternary ammonium compounds.

5.. A'process fontlie preparation of thermoset, inf-usible-;= solvent in'soluble polymers of styrene suitable) as. protective coatings;v which comprises; heating a thermoplastiqfusible, solvent soluble. copolymer of fl2 'parts of styrene and; Sparta. of acrylic, acid and 20 parts of methyl acrylate, with oneimol of ,diphenylolpropane diglycidyl ether for each two; freegcarboxylic acid,- groups of the co p ymer. t atcmneraiure of ab u l50r- 1 nd in the presenceof. at:least-,0.5%, by weight of the lymer a r a or anic; ba .e a i l ct qt from te group consistingof amines. and; quaternary ammonium. compounds. I A p 6. Thermoset, infusible; solvent insoluble poly,- mers of styrene as prepared by-the 'pr'ocesslse't forth in claim 1.

7. Thermoset, infusible, solvent insoluble polymer of styrene as prepare d by the process set 8; A coating composition adapted" for being hardened into an, infusible, solvent insoluble; grease andj alkali'resistant-film on'baking at a temperature of-aboutl'SOfiC. afterapplicat-ion,

comprising essentially a *linear thermoplastic copolymer ofmore thamfill parts of-styrene and at least 5 parts of an acid selected fiom'thegroup consistingof-acr'ylijc acid and methacrylic acid and at least' 15 parts of a lower alkyl ester of acrylic acid',;the'-tetal* parts being-ice, in adminturew th one inol of 'diphenylolpropane cl-iglycidyl ether Tor each-two frei carboxylic: acid groups of th'e copolymer-i and at least: 0.5%. bwweightf ofi selected from the group consisting of amines and quaternary ammonium compounds.

9. A coating composition adapted for being hardened into an infusible, solvent insoluble, grease and alkali resistant film on baking at a temperature of about 150 C, after application, comprising essentially a linear thermoplastic copolymer of from 70 to 80 parts of styrene and from 5 to 15 parts of an acid selected from the group consisting of acrylic acid and methacrylic acid and from 15 to 20 arts of a lower alkyl ester of acrylic acid, the total parts being 100, in admixture with one mol of diphenylolpropane diglycidyl' ether for each two free carboxylic acid groups ofthe copolymer and at least 0.5%} by weight of the copolymer, of an organic basic catalyst selected from the group consisting of amines and quaternary ammonium compounds.

10. A coating composition adapted for being hardened into an infusible, solvent insoluble, greaserand alkali resistant film on baking at "a temperature of about 150 C. after application,

GORDON HART SEGALL. JOHN FRANCIS CLEMOW DIXON.

REFERENCES CITED The following references are of record in the file of this patent:

v UNITED STATES PATENTS Number Name Date 7 2,131,120 Schlack Sept. 27, 1938 20 2,527,806 Foster Oct. 31, 1950 2,530,983 Minter Nov. 21, 1950 

3. A PROCESS FOR THE PREPARATION OF THERMOSET, INFUSIBLE, SOLVENT INSOLUBLE POLYMERS OF STYRENE SUITABLE AS PROTECTIVE COATINGS, WHICH COMPRISES HEATING A THERMOPLASTIC, FUSIBLE, SOLVENT SOLUBLE COPOLYMER OF MORE THAN 50 PARTS OF STYRENE AND AT LEAST 5 PARTS OF AN ACID SELECTED FROM THE GROUP CONSISTING OF ACRYLIC ACID AND METHACRYLIC ACID AND AT LEAST 15 PARTS OF A LOWER ALKYL ESTER OF ACRYLIC ACID, THE TOTAL PARTS BEING 100, WITH ONE MOL OF DIPHENYLOLPROPANE DIGLYCIDYL ETHER FOR EACH TWO FREE CARBOXYLIC ACID GROUPS OF THE COPOLYMER, AT A TEMPERATURE OF ABOUT 150* C. AND IN THE PRESENCE OF AT LEAST 0.5%, BY WEIGHT OF THE COPOLYMER, OF AN ORGANIC BASIC CATALYST SELECTED FROM THE GROUP CONSISTING OF AMINES AND QUATERNARY AMMONIUM COMPOUNDS. 